The present invention relates to a process for inhibiting or eliminating the growth of microorganisms in pesticide suspensions. More particularly, the process of the present invention includes the addition of a combination of peracetic acid, hydrogen peroxide and water, to the pesticide suspension. Further, the process of the present invention includes the application of the peracetic acid, hydrogen peroxide, and water combination to the interior surface of the vessel in which the pesticide suspension is contained. Still further, the process of the present invention includes the application of the peracetic acid, hydrogen peroxide, and water combination to a surface in which the pesticide suspension is in contact.
A pesticide suspension is a homogeneous mixture of small solid particles of pesticide suspended in a liquid medium. The growth of microorganisms in the pesticide suspension can cause a solid precipitate to form and therefore, a loss of homogeneity in the mixture. Formation of the precipitate and the loss of homogeneity can result in product failure due to non-uniform applications of the pesticide, and plugging of strainers and nozzles used with the application equipment.
Peracetic acid and hydrogen peroxide solutions are known in the art. French Patent No. 2,462,425, discloses a process for the preparation of stable dilute solutions of peracetic acid. U.S. Pat. No. 4,051,049 discloses a formulation having from 0.5 to 20% peracetic acid, 25 to 40% hydrogen peroxide and from 0 to 5% of an anionic surfactant. U.S. Pat. No. 5,656,302 discloses stable microbicidal formulations comprising a considerably greater quantity of peracetic acid plus acetic acid than the quantity of hydrogen peroxide.
Further, the use of peracetic acid and hydrogen peroxide solutions for purposes of sterilization and disinfection are well known. For example, commercial solutions of noncorrosive time-stable carboxylic peracids, particularly peracetic acid, are known to be useful for the sterilization and microbiological disinfection of equipment in the food industry (see U.S. Pat. No. 4,587,264). In addition to the food industry, commercial peracetic acid and hydrogen peroxide solutions are also known disinfectants in the medical and dental professions. U.S. Pat. No. 5,508,046 describes novel stable microbicides comprising hydrogen peroxide, peracetic acid, acetic acid, purified water, and a stabilizer having anticorrosive properties, for use in the sterilization of surgical and dental instruments.
Moreover, the commercial peracetic acid solution Minncare was developed by the Minntech Corporation and is used as a disinfectant in providing protection against short- and long-term bacterial problems for reverse osmosis membranes and their associated distribution systems.
To reduce or eliminate the growth of microorganisms in pesticide suspensions, a practice of combining or formulating the pesticide compounds with a preservative has developed in the art. U.S. Pat. No. 5,283,231 describes formaldehyde, sodium benzoate, glutaraldehyde, and pentachlorophenol, as effective preservatives to prevent microbial spoiling in low-melting dinitroaniline pesticide suspensions.
Not all preservatives are effective against all types of microorganisms, in all pesticide suspensions. Thus, there is a need in the art to determine specific preservatives that are effective in a particular flowable aqueous pesticide composition (i) to reduce or eliminate the growth of microorganisms, (ii) while being easy to handle during preparation and use, and (iii) maintaining an excellent shelf-life even during extended storage.
It is an object of the present invention to provide a process for inhibiting or eliminating the growth of microorganisms in pesticide suspensions. This and other objects which will be apparent to those skilled in the art are accomplished by the (i) addition of a combination of peracetic acid, hydrogen peroxide, and water to the pesticide suspension, or (ii) application of the peracetic acid, hydrogen peroxide, and water combination to the interior surface of the vessel in which the pesticide suspension is contained, or (iii) application of the peracetic acid, hydrogen peroxide, and water combination to a surface which the pesticide suspension is in contact. The peracetic acid, hydrogen peroxide, and water combination is present in the water-based pesticide suspension in an amount of from about 0.05% to about 1.0% by weight of the suspension.
The process of the present invention comprises (i) the addition of a combination of a peracetic acid, hydrogen peroxide, and water to a pesticide formulation; (ii) the application of a combination of peracetic acid, hydrogen peroxide, and water to the interior surface of the vessel in which the pesticide formulation is contained; and (iii) the application of a combination of peracetic acid, hydrogen peroxide, and water to a surface in which the pesticide formulation is in contact.
In the present invention, the peracetic acid, hydrogen peroxide, and water combination (xe2x80x9cbiocide combinationxe2x80x9d) is used to reduce or eliminate the growth of microorganisms in the pesticide formulation. Biocides are well known in the art. Typical commercial biocides include: (i) Minncare, which is a peracetic acid solution used as a disinfectant for reverse osmosis membranes; (ii) Proxel GXL, which is an aqueous solution of dipropylene glycol and 17% 1,2-benzisothiazolin-2-one; and (iii) Legend MK, which includes 1.15% 5-chloro-2-methyl-4-isothiazolin-3-one and 0.35% 2-methyl-4-isothiazolin-3-one.
In the present invention, a biocide combination is added to a pesticide suspension to reduce or eliminate the growth of microorganisms in the suspension. The biocide combination constitutes from about 3.0% to about 7.0% by weight of peracetic acid, from about 19.0% to about 25.0% by weight of hydrogen peroxide, and the remainder, from about 68% to about 78% by weight, is water. The total composition by weight of the peracetic acid, hydrogen peroxide, and water, is 100%. The biocide combination is added to the pesticide suspension in an amount such that it comprises from about 0.05% to about 1.0% by weight of the pesticide suspension.
The pesticide is selected from the group consisting of an insecticide, a fungicide, and a herbicide. Suitable insecticides include the heterocyclic compounds described in U.S. Pat. Nos. 5,852,012; 5,719,146; 4,849,432; and 4,742,060; which are incorporated herein by reference. Further, in a preferred embodiment of the invention, the insecticide is a chloronicotinyl or a chlorothiazole. Moreover, insecticides of the following general formulas (I), (II) and (Ill) are most preferred. 
A preferred fungicide is tebuconazole, and a preferred herbicide is metribuzin.
Further, in an embodiment of the present invention, the biocide combination is applied to the interior surface of the vessel in which the pesticide formulation is contained. The method of application may be performed using any manual or automated means known in the art.
In another embodiment of the present invention, the biocide combination is applied to a surface in which the pesticide suspension is in contact. The method of application to the surface may be accomplished using any manual or automated means known in the art.
Having thus described our invention, the following examples are given as being illustrative thereof; and they are in no way meant to be limiting of the specification and the claims. All weights and percentages given are parts by weight or percentages by weight, unless otherwise indicated.